When I was a teenager, one of the service projects we did at our church was making yarn out of plastic grocery sacks. The yarn would be collected and shipped to Africa where the women could crochet and/or knit the yarn into products they could sell.
I’m learning how to crochet right now so I thought some grocery sack yarn would be a great way to learn without going through tons of normal yarn. This Is how I make my grocery sack yarn: